Capgras delusion

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The Capgras delusion or Capgras' syndrome is a rare disorder in which a person holds a delusional belief that an acquaintance, usually a close family member or spouse, has been replaced by an identical looking impostor. Capgras delusion is classed as a delusional misidentification syndrome, a class of delusional beliefs that involves the misidentification of people, places or objects. It can occur in acute, transient, or chronic forms.

The delusion is most common in patients diagnosed with schizophrenia, although it can occur in a number of conditions including after brain injury and dementia.[1] Although Capgras is commonly called a syndrome, because it can occur as part of, or alongside, various other disorders and conditions some researchers have argued that it should be considered as a symptom, rather than a syndrome or classification in its own right.

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[edit] History

It is named after Joseph Capgras (1873-1950), a French psychiatrist who first described the disorder in a 1923 paper by Capgras and Reboul-Lachaux.[2][3] They used the term l'illusion des sosies (the illusion of doubles) to describe the case of a French woman who complained that various "doubles" had taken the place of people she knew. However, the term illusion has a subtly different meaning from delusion in psychiatry so "Capgras delusion" is used as a more suitable name.

[edit] Presentation

This case is taken from a 1991 report by Passer and Warnock[4]:

Mrs. D, a 74-year old married housewife, recently discharged from a local hospital after her first psychiatric admission, presented to our facility for a second opinion. At the time of her admission earlier in the year, she had received the diagnosis of atypical psychosis because of her belief that her husband had been replaced by another unrelated man. She refused to sleep with the imposter, locked her bedroom and door at night, asked her son for a gun, and finally fought with the police when attempts were made to hospitalize her. At times she believed her husband was her long deceased father. She easily recognized other family members and would misidentify her husband only.

[edit] Causes

Some of the first clues to the possible causes of Capgras delusion were suggested by the study of brain injured patients who had developed prosopagnosia. In this condition, patients are unable to consciously recognise faces despite being able to recognise other types of visual objects. However, a 1984 study by Baur showed that even though conscious face recognition was impaired, patients with the condition showed automatic arousal (measured by a galvanic skin response measure) to familiar faces,[5] suggesting that there were two pathways to face recognition - one conscious and one unconscious.

In a 1990 paper published in the British Journal of Psychiatry,[6] psychologists Hadyn Ellis and Andy Young hypothesised that patients with Capgras delusion may have a 'mirror image' of prosopagnosia, in that their conscious ability to recognise faces was intact, but they might have damage to the system which produces the automatic emotional arousal to familiar faces. This might lead to the experience of recognising someone, while feeling something wasn't 'quite right' about them.

In 1997 Hadyn Ellis and colleagues published a study of five patients with Capgras delusion (all diagnosed with schizophrenia) and confirmed that although they could consciously recognise the faces, they did not show the normal automatic emotional arousal response.[7] The same year Hirstein and Ramachandran published a paper on a single case of a patient with Capgras delusion after brain injury that reported similar findings.[8]

It is likely that this is not the only impairment which is needed for Capgras delusion to form, however, as exactly this pattern has been reported in other patients who show no signs of delusions.[9] Ellis and colleagues suggested that a 'second factor' is therefore needed, to explain why this unusual experience is transformed into a delusional belief. This 'second factor' is thought to be an impairment in reasoning, although no definitive impairment has been found which could explain all cases.[10]

[edit] In fiction

Capgras Syndrome plays an important part in Richard Powers' 2006 novel The Echo Maker.

Situations in which the protagonist (and the audience) knows that their acquaintances have been replaced by spies, aliens or monsters while the rest of the people think the protagonist insane appear in several works of horror and science fiction. Well-known examples include Invasion of the Body Snatchers, The Stepford Wives, Total Recall, The Astronaut's Wife, Impostor and The Faculty.

The film adaptation of The Addams Family offers a unique perspective on the situation in which a character (Uncle Fester) thought to be an imposter actually turns out to be the true individual, who assumed he was playing a role as a result of amnesia and psychological manipulation.

An example of Capgras delusion (and possibly a parody of the latter genre) occurs in The Outward Urge where an astronaut develops the delusion that his colleague is a Martian.

On one episode of The Simpsons, Homer is replaced by an imposter and the family members are hinted to suspect the false Homer.

[edit] See also

[edit] References

  1. ^ Forstl, H.; Almeida, O.P.; Owen, A.M.; Burns, A.; & Howard, R. (1991). Psychiatric, neurological and medical aspects of misidentification syndromes: a review of 260 cases. Psychological Medicine 21 (4) 905–910.
  2. ^ Capgras, J. & Reboul-Lachaux, J. (1923). Illusion des sosies dans un delire systematise chronique. Bulletin de la Societe Clinique de Medicine Mentale 2 6–16.
  3. ^ Ellis, H.D.; Whitley, J.; & Luaute, J.P. (1994). Delusional misidentification. The three original papers on the Capgras, Frégoli and intermetamorphosis delusions (Classic Text No. 17). History of Psychiatry 5 (17) 117–146.
  4. ^ Passer, K.M. & Warnock, J.K. (1991). Pimozide in the treatment of Capgras' syndrome. A case report. Psychosomatics 32 (4) 446–448.
  5. ^ Bauer, R.M. (1984) Autonomic recognition of names and faces in prosopagnosia: a neuropsychological application of the guilty knowledge test. Neuropsychologia 22, 457–469.
  6. ^ Ellis, H. D., & Young, A. W. (1990) Accounting for delusional misidentifications. Br J Psychiatry, 157, 239-248.
  7. ^ Ellis, H. D., Young, A. W., Quayle, A. H., & De Pauw, K. W. (1997) Reduced autonomic responses to faces in Capgras delusion. Proc R Soc Lond B Biol Sci, 264, 1085-1092.
  8. ^ Hirstein, W., & Ramachandran, V. S. (1997) Capgras syndrome: a novel probe for understanding the neural representation of the identity and familiarity of persons. Proc R Soc Lond B Biol Sci, 264, 437-444."
  9. ^ Tranel D, Damasio H, Damasio A (1995) Double dissociation between overt and covert face recognition. Journal of Cognitive Neuroscience, 7, 425-432.
  10. ^ Davies, M., Coltheart, M., Langdon, R., & Breen, N. (2001) Monothematic delusions: Towards a two-factor account. Philosophy, Psychiatry, and Psychology, 8, 133-158.
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